This invention relates in general to the field of television systems, and more particularly, to the field of memory management and application versioning in a communication terminal.
Historically, television services have been comprised of analog broadcast audio and video signals. Cable television systems now receive broadcasts and retransmit them with other programming to subscribers over land-line networks, typically comprising fiber optic cable and/or coaxial cable. With the recent advent of digital transmission technology, cable television systems are now capable of providing much more than the traditional analog broadcast video. In addition, two-way and advanced one-way communications between a subscriber and a cable system headend are now possible.
In implementing enhanced programming, the home communications terminal (xe2x80x9cHCTxe2x80x9d), otherwise known as the settop box, has become an important computing device for accessing video services and navigating a subscriber through a maze of services available. In addition to supporting traditional analog broadcast video functionality, digital HCTs (or xe2x80x9cDHCTsxe2x80x9d) now also support an increasing number of services that are not analog, but rather digital; are not basic broadcast, but rather two-way communication such as video-on-demand; and are not basic video, such as e-mail or web browsers. These are all in addition to the host of other television services that are increasingly being demanded by consumers, examples of which include audio and audio/visual programming, advance navigation controls, impulse pay-per-view technology, and on-line commerce. In addition to the interactive services, the increased bandwidth available through a digital television system has made it possible for a subscriber to have access to hundreds, or even thousands, of channels and/or services. Thus, in order to provide these more powerful and complex features, the simple conventional channel abstractions need to be extended beyond those that have traditionally been provided.
Each HCT and DHCT (collectively hereinafter xe2x80x9cDHCTxe2x80x9d) is typically connected to a cable or satellite television network. The DHCTs generally include hardware and software necessary to provide the functionality of the digital television system at the subscriber""s site. Preferably, some of the software executed by a DHCT is downloaded and/or updated via the cable television network. Each DHCT typically includes a processor, a communication component and memory, and is connected to a television or other display device, such as a personal computer. While many conventional DHCTs are stand-alone devices that are externally connected to a television, a DHCT and/or its functionality may be integrated into a television or personal computer, as will be appreciated by those of ordinary skill in the art.
As more and more services and applications are made available, it becomes increasingly important to properly manage limited client resources. Because the memory contained in the DHCT is typically finite, only a limited number of services and applications may be downloaded to and stored on the DHCT at any given time. Once the memory of the DHCT becomes full with applications and other data, a DHCT may be unable to download additional files or applications for the user due to the memory incapacity. For the user, this scenario can result in a denial of a particular service, or worse, a complete failure of the DHCT due to a memory error. As the number of applications available to a user continues to grow, a conventional DHCT may be unable to implement many of these applications once the memory becomes full for the first time. The cost of additional DHCT memory may be prohibitive for the system operator or subscriber; in any case memory is always finite and out of memory conditions will occur.
Additionally, as services and applications are updated by system operators of the cable television systems, the versions already contained on the DHCTs can become outdated and unsupported. While the cable systems may support old versions of applications for a short period of time, eventually these applications may fail when activated by the DHCT because of their incompatibility with the cable television system headend. As a result, once the memory capacity of a conventional DHCT has become full, then not only is that DHCT typically limited to those applications contained in memory, but also those applications may have limited lifespan as updated versions are released over the network by the cable television system.
Briefly described, the preferred embodiment of the present invention provides a system and method for managing memory in a DHCT coupled via a communication port to a server device by enabling the DHCT to prioritize application access to memory and to further handle out-of-memory situations while executing on the DHCT a plurality of applications downloaded from the server device. In one implementation, prior to downloading an application, the DHCT determines an amount of memory capacity required to execute an application client after the application client is downloaded from the server device. The DHCT then attempts to allocate the memory capacity from a private heap of the memory to the application client. If unsuccessful, the DHCT attempts to allocate the memory capacity from a system heap of the memory to the application client. If memory cannot be allocated from the system heap, the DHCT purges data contained in the memory according to a dynamic list of priorities to create memory capacity in the memory for the application client. Once sufficient memory capacity has been created, it is allocated to the application client after the application client is downloaded to the DHCT.
Further, while the application is executing and actively providing a service, its request for memory may exceed that currently available on the DHCT. The DHCT then follows the same protocol mentioned above to make memory available for the application. This process can include asking other applications to free unneeded or lower priority memory and if still not enough room to free higher priority memory. Finally, other applications that are not currently providing services to the user may be unloaded to meet the memory request of the application with which the user is currently interacting.
In addition, according to the preferred embodiment, a version table is also periodically downloaded from the server device (headend) and referenced each time an application is activated to ensure that the correct version is being activated, otherwise prompting the DHCT to unload the old version and download the newest version of the application.
One advantage of the preferred embodiment of the present invention is that it solves the problem of limited memory in the DHCT by enabling the DHCT to create memory capacity to load and execute new applications desired by a subscriber without failing or crashing.
Another advantage of the preferred embodiment of the present invention is that it enables applications of higher priority to be the last applications to be removed from the DHCT when making memory available to an application to be downloaded.
Another advantage of the present invention is that memory capacity is properly maintained through systematic downloading of updated versions of applications as made available by the headend server.
Other advantages of the present invention will become apparent to one with skill in the art upon examination of the following drawings and detailed description.